June 2005

1

M9999-062105

MIC4574

Micrel, Inc.

MIC4574

200kHz Simple 0.5A Buck Regulator

General Description

The MIC4574 is a series of easy to use fixed and adjustable

BiCMOS step-down (buck) switch-mode voltage regulators.

The 200kHz MIC4574 duplicates the pinout and function of

the 52kHz LM2574. The higher switching frequency may

allow up to a 2:1 reduction in output filter inductor size.

The MIC4574 is available in 3.3V, and 5V fixed output

versions or a 1.23V to 20V adjustable output version. Both

versions are capable of driving a 0.5A load with excellent line

and load regulation.

The feedback voltage is guaranteed to ±2% tolerance for

adjustable versions, and the output voltage is guaranteed to

±3% for fixed versions, within specified voltages and load

conditions. The oscillator frequency is guaranteed to ±10%.

In shutdown mode, the regulator draws less than 200µA

standby current. The regulator performs cycle-by-cycle cur-

rent limiting and thermal shutdown for protection under fault

conditions.

This series of simple switch-mode regulators requires a

minimum number of external components and can operate

using a standard series of inductors. Frequency compensa-

tion is provided internally.

The MIC4574 is available in the DIP (N) package and is rated

over the industrial temperature range.

Data sheets and support documentation can be found on

Micrel’s web site at www.micrel.com.

Typical Application

C1

47µF

35V

D1

1N5819

C2

220µF

16V

L1

100µH

SGND

FB

SW

MIC4574-5.0BN

SHDN

8V to 24V

5.0V/0.5A

PGND

24

1

7

3

5

Shutdown

Enable

Fixed Regulator

Features

•Fixed 200kHz operation

• 3.3V, 5V, and adjustable output versions

•Voltage over specified line and load conditions:

Fixed version: ±3% max. output voltage

Adjustable version: ±2% max. feedback voltage

•Guaranteed 0.5A switch current

•Wide 4V to 24V input voltage range

•Wide 1.23V to 20V output voltage range

•Requires minimum external components

•< 200µA typical shutdown mode

• 75% efficiency (adjustable version > 75% typ.)

•Standard inductors and capacitors are

25% of typical LM2574 values

•Thermal shutdown

•Overcurrent protection

• 100% electrical thermal limit burn-in

Applications

•Simple high-efficiency step-down (buck) regulator

•Efficient preregulator for linear regulators

•On-card switching regulators

•Positive-to-negative converter (inverting buck-boost)

• Isolated flyback converter using minimum external

components

•Negative boost converter

Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com